三峡地区香溪河流域不同树种叶片凋落物的分解

在香溪河流域1160m、930m、658m 3个海拔梯度,利用网袋法,研究黄栌（Cotinus coggygria var.pubescens）、五裂槭（Acer oliverianum）、扇叶槭（Acer flabellatum）3个树种叶片凋落物在河流中和河岸陆地的分解速度和分解动态.结果表明,分解进行90d,叶片凋落物干重流失率为13﹪～74﹪.凋落物的干物质重量流失速度符合指数衰减方程（p＜0.05）.叶片凋落物分解前3d干物质迅速淋洗,在河流中,凋落物干重淋洗率为9﹪～18﹪,河岸陆地为4﹪～9﹪.叶片凋落物在河流中分解30d后,分解速度趋于稳定.叶片凋落物在河岸陆地分解90d的过程中,分解速度呈现一定的波动性.黄栌叶片的分解为中速（分解系数k值为0.0043～0.0079d^-1）,显著慢于五裂槭和扇叶槭.五裂槭和扇叶槭作为同属物种,叶片的分解速度之间没有显著差异,在海拔1160m和930m河流中为快速分解（分解系数k值为0.0101～0.0140d^-1）,在海拔658m河流中为中速分解（分解系数k值分别为0.0084d^-1、0.0078d^-1）.扇叶槭在河岸陆地的分解速度在3个海拔间差异较小,干物质流失均缓慢,分解速度（分解系数k为0.0027～0.0036d^-1）显著低于河流.方差分析结果表明,海拔梯度与叶片凋落物的分解速度之间没有显著相关性（p＞0.05）.河流中叶片凋落物在春夏季节的快速分解对底栖生物群落和下游养分循环有重要作用.     

香溪河流域一条一级支流河岸林凋落物季节动态

对神农架南坡的一条一级支流河岸林的凋落物进行了一年的连续收集研究。结果表明：凋落物干重年输入量为438．72g／m^2,其中树叶凋落物是凋落物的主要成分,占整个凋落物年产量的84％。凋落物的输入明显存在季节性的时间格局。凋落物在秋季的产量占全年产量的75％,春季占6．2％,夏季占13．6％,冬季为5．5％。凋落物组成中,树叶和花果的产量显示出季节变化的趋势;枝条的产量并未显示出明显的季节趋势。在秋季,树叶的产量占全年树叶总量的83％;枝条最高值出现于秋季,产量占全年总员的29％;花果在整个凋落物中所占比重分小,最高值出现在夏季,占年产量的63％。着生藻类的密度月际间的变化较大,存在着显著的差异。最大值与最小值的出现月份与凋落物最大、最低值的出现月份相同。通过统计分析表明,着生藻类的密度变化与凋落物和树叶凋落物的动态具有明显的相关性。     

香溪河流域河流中树叶分解速率的比较研究

应用分解网袋法,对神农架地区的1条1级支流河岸林4种乔木树种的树叶凋落物进行了连续90d的分解研究。结果表明,不同树种树叶干重的损失程度不一样,华西枫杨,连香树树叶干重损失达77%,71%;而米心水青冈和多脉青冈树叶干重损失为43%和42%,利用指数方程Wt=W0e^-kt对4种树叶凋落物的干重损失过程进行拟合,效果较好,根据分解速率值的大小,将华西枫杨,连香树划分为快组,米心水青冈和多脉青冈树叶干重损失为43%和42%,利用指数方程Wt=W0e^-kt对4种树叶凋落物的干重损失过程进行拟合,效果较好,根据分解速率值的大小,将华西枫杨,连香树划分为快组,米心水青冈和多脉青冈为中等组,收集到无脊椎动物22种,分属于3纲、6目、21科,在不同时期,不同植物种类叶袋中无脊椎动物的数量各不相同,可能与树叶中营养成分的不同有关,在早期分解阶段。无脊椎动物数量较多,个体体长较短;在分解中后期,个体绝对数量减少,但个体体长增加。     

绵阳官司河流域主要森林类型凋落物含量及动态变化

对绵阳官司河流域代表性森林——桤柏混交林、柏木纯林、松栎混交林和松柏混交林的凋落物量、组成特征和季节动态变化及其凋落物中N、P、K含量进行了定位观测和研究,结果表明：其年均凋落物量分别为4．229（3．732—4．828）、5．133（4．215—6．545）、5．701（5．133—6．642）t·hm^-2和5．351（4．762—5．854）t·hm^-2;叶、枝、花果、松皮和杂物的比例分别为72．1：8．9：11．9：0：7．1、75．4：9．0：9．0：0：6．5、79．7：11．0：6．3：0．5：2．4和60．4：9．5：16．0：7．5：6．5;灌木凋落量分别占总凋落量的16．4％、1．5％、9．5％和12．1％;凋落物的年变化规律为：桤柏混交林和柏木林主要集中在生长季,松柏混交林为双峰型,出现在生长季早期和休眠期,松栎混交林为单峰型,为12月份;凋落物中N、P、K元素含量以N素最高,其次是K素,P素最少,N、P、K总量分别为62．702、70．596、79．228kg·hm^-2a^-1和80．011kg·hm^-2·a^-1。     

青冈常绿阔叶林凋落物分解过程中营养元素动态

应用分解袋法研究了浙江建德青冈常绿阔叶林凋落物分解过程中的养分动态.结果表明,在2a的分解过程中,各凋落物元素的年均释放率为C 27.91%～44.06%,N 30.77%～39.58%,P 33.33%～42.86%,K 42.31%～48.19%,Ca 18.67%～36.22%,Mg 35.71%～47.22%,Mn 25.00%～37.50%,Cu 3.80%～16.21%,Zn -17.52%～26.60%.K和Mg流动性较大,Zn、Cu和Ca相对稳定,P、Zn、Cu、Ca、N和Mn在分解过程中有不同程度累积.干物质残留量与N、Ca、Mn、Cu和Zn的残留率呈负相关,与C、K和Mg呈正相关.C、N主要以线性衰减方式释放,P和Mg主要以复合函数方式释放,K主要以对数方式释放,Ca、Mn、Cu和Zn残留率具有3种以上的最优模型.Cu、Zn、Ca和Mn对干物质的分解有促进作用.C：N比是预示分解速率的最理想指标.枯叶中C：N比对于N固持和矿化的分界值在20：1左右,C：P比对于P的净矿化的临界值在600：1左右.     

川中人工纯柏林凋落物分解动态研究

对柏木人工纯林的渊落物有机碳和一些营养元素的分解和释放过程的研究表明,柏木凋落物中有机碳和营养元素的矿化非常缓慢,凋落物有机碳的半减期是33周,氮素矿化半减期是433周,磷矿化半减期是10周,钾矿化半减期是24周,钙矿化半减期是86周,镁矿化半减期是12周。柏木早期生长缓慢、成林困难主要是受氮素不足的制约。在林分改造和营林中适当增加阔叶速生树种,改善凋落物性质．对促进凋落物分解和养分周转、改善土壤养分状况、提高柏木人工林的生态和经济效益是很必要的。     

暖温带地区主要树种叶片凋落物分解过程中主要元素释放的比较

应用分解网袋法对暖温带落叶阔叶林内分布较为优势的辽东栎（Quercus liaotungensis)、五角枫（Acermono)、蒙椴（Tilia mongolica)、糠椴（T.mandshurica)等4种植物叶片凋落物第一年的分解速率损失过程基本符合Olson的指数降解模型。4种凋落物的分解速率（凋落物的年重量损失）依次为五角枫＞糠椴＞蒙椴＞辽乐栎。N、P、Na、Fe、Cu、Mn在几种凋落物残留物中各自有不同程度的富集。C、K含量显著单调下降,其它几种元素含量变化不太规律。可以看出,元素的初始含量对其释放速率有很大影响,当微生物固持作用使C与其它元素比升高到某一阈值时,元素开始释放;初始含量较高的元素则从最初开始释放。高含量的木质素对元素的净释放有一定抑制作用,而在凋落物分解初期影响不大。     

红松阔叶混交林凋落物-土壤动物-土壤系统中N、P、K的动态特征

根据对小兴安岭凉水国家级自然保护区红松阔叶混交林的凋落物、土壤动物和土壤2a的连续采样及测定主要营养元素N、P、K的含量,研究凋落物-土壤动物-土壤系统中主要营养元素在各分室的动态变化,并通过比较主要营养元素在不同分室中的分异,进而分析了土壤动物在该系统营养循环中的作用。结果表明,研究区内不同凋落叶分解过程中元素含量的动态变化比较复杂,阔叶落叶中营养元素含量的变化大于针叶落叶,但不同凋落叶在分解过程中的元素损失量之间的差异不显著。在研究时段,腐殖土层各种营养元素的含量高于土壤层;蚯蚓、蜈蚣和马陆大型土壤动物体内的营养元素含量之间差别较大,其中蚯蚓体内全N含量最高,而马陆体内全P含量最高,蜈蚣则全K含量最高。土壤动物和土壤中营养元素含量的动态变化和凋落叶中的变化趋势不同。N和P在土壤动物分室中表现出一定的富集,而K的富集不明显。土壤动物可以通过其新陈代谢活动加速凋落物-土壤动物-土壤系统中营养元素的循环速率。不同凋落物分解过程中养分含量变化复杂可能是由于不同凋落物种类特性差异造成的。土壤动物在营养元素循环,尤其是N、P元素循环中具有重要意义。     

氮、磷养分有效性对森林凋落物分解的影响研究进展

通过对相关研究文献的综述结果表明,氮(N)和磷(P)是构成蛋白质和遗传物质的两种重要组成元素,限制森林生产力和其他生态系统过程,对凋落物分解产生深刻影响。大量的凋落物分解试验发现在土壤N有效性较低的温带和北方森林,凋落物分解速率常与底物初始N浓度、木质素/N比等有很好的相关关系,也受外源N输入的影响;而在土壤高度风化的热带亚热带森林生态系统中,P可能是比N更为重要的分解限制因子。然而控制试验表明,N、P添加对凋落物分解速率的影响并不一致,既有促进效应也有抑制效应。为了深入揭示N、P养分有效性对凋落物分解的调控机制,"底物的C、N化学计量学"假说、"微生物的N开采"假说以及养分平衡的理论都常被用于解释凋落物分解速率的变化。由于微生物分解者具有较为稳定的C、N、P等养分需求比例,在不同的养分供应的周围环境中会体现出不同的活性,某种最缺乏的养分可能就是分解的最重要限制因子。未来的凋落物分解研究,应延长实验时间、加强室内和野外不同条件下的N、P等养分添加控制试验,探讨驱动分解进程的微生物群落结构和酶活性的变化。     

典型喀斯特峰丛洼地植被群落凋落物C∶N∶P生态化学计量特征

为了解典型喀斯特峰丛洼地植被群落凋落物养分空间分异以及其生态化学计量特征,分析了4个不同演替阶段植被凋落物现存量、C、N、P含量及C、N、P元素比值关系在不同坡位间的差异。结果表明:(1)不同演替阶段群落凋落物现存量和C、N、P含量、N ∶ P值随植被正向演替而升高;C ∶ N值和C ∶ P值随植被正向演替而下降。(2)凋落物C含量、C ∶ N值、C ∶ P值和N ∶ P值在不同坡位表现为上坡位较高、下坡位较低;P含量的变化规律与之相反,N含量则没呈现很明显的规律性(P<0.05)。典范对应分析(CCA)结果表明演替阶段和坡位对凋落物积累、养分分布和存储影响最大,坡度、坡向和裸岩率也有较大影响。(3)N ∶ P值是制约凋落物分解和养分循环的重要因素。凋落物在P素较低的情况下具有较高的N及木质素含量(即较高的N ∶ P值),分解速率较低,较低的N ∶ P值使凋落物更易分解。N素在3个坡位的不显著差异以及P素的显著差异反映了P含量波动对喀斯特峰丛洼地植被凋落物N ∶ P值和分解速率变化的影响。推测下坡位及幼龄林群落由于具有较低的N ∶ P值,其凋落物分解速率相对较快,养分的存储量较少。因此,上坡位、成熟林群落的凋落物有利于积累养分。     

Litter Decomposition and Nutrient Dynamics in a Phosphorus Enriched Everglades Marsh

A field study was conducted in a nutrient-impacted marsh in Water Conservation Area 2A (WCA-2A) of the Everglades in southern Florida, USA, to evaluate early stages of plant litter (detritus) decomposition along a well-documented trophic gradient, and to determine the relative importance of environmental factors and substrate composition in governing decomposition rate. Vertically stratified decomposition chambers containing native plant litter (cattail and sawgrass leaves) were placed in the soil and water column along a 10-km transect coinciding with a gradient of soil phosphorus (P) enrichment. Decomposition rate varied significantly along the vertical water–soil profile, with rates typically higher in the water column and litter layer than below the soil surface, presumably in response to vertical gradients of such environmental factors as O₂ and nutrient availability. An overall decrease in decomposition rate occurred along the soil P gradient (from high- to low-impact). First-order rate constant (k) values for decomposition ranged from 1.0 to 9.2 × 10⁻³ day⁻¹ (mean = 2.8 ×10⁻³ day⁻¹) for cattails, and from 6.7 × 10⁻⁴ to 3.0 ×  10⁻³ day⁻¹ (mean = 1.7 ×  10⁻³ day⁻¹) for sawgrass. Substantial N and P immobilization occurred within the litter layer, being most pronounced at nutrient-impacted sites. Nutrient content of the decomposing plant tissue was more strongly correlated to decomposition rate than was the nutrient content of the surrounding soil and water. Our experimental results suggest that, although decomposition rate was significantly affected by initial substrate composition, the external supply or availability of nutrients probably played a greater role in controlling decomposition rate. It was also evident that nutrient availability for litter decomposition was not accurately reflected by ambient nutrient concentration, e.g., water and soil porewater nutrient concentration.     

Interactions between Litter Lignin and Nitrogenitter Lignin and Soil Nitrogen Availability during Leaf Litter Decomposition in a Hawaiian Montane Forest

Previous work in a young Hawaiian forest has shown that nitrogen (N) limits aboveground net primary production (ANPP) more strongly than it does decomposition, despite low soil N availability. In this study, I determined whether (a) poor litter C quality (that is, high litter lignin) poses an overriding constraint on decomposition, preventing decomposers from responding to added N, or (b) high N levels inhibit lignin degradation, lessening the effects of added N on decomposition overall. I obtained leaf litter from one species, Metrosideros polymorpha, which dominates a range of sites in the Hawaiian Islands and whose litter lignin concentration declines with decreasing precipitation. Litter from three dry sites had lignin concentrations of 12% or less, whereas litter from two wet sites, including the study site, had lignin concentrations of more than 18%. This litter was deployed 2.5 years in a common site in control plots (receiving no added nutrients) and in N-fertilized plots. Nitrogen fertilization stimulated decomposition of the low-lignin litter types more than that of the high-lignin litter types. However, in contrast to results from temperate forests, N did not inhibit lignin decomposition. Rather, lignin decay increased with added N, suggesting that the small effect of N on decomposition at this site results from limitation of decomposition by poor C quality rather than from N inhibition of lignin decay. Even though ANPP is limited by N, decomposers are strongly limited by C quality. My results suggest that anthropogenic N deposition may increase leaf litter decomposition more in ecosystems characterized by low-lignin litter than in those characterized by high-lignin litter. Received 26 October 1999; accepted 2 June 2000.     

Short- and Long-term Tannin Induced Carbon, Nitrogen and Phosphorus Dynamics in Corsican Pine Litter

Pine litter amended with either tannic acid (TA) or condensed tannins (CTs) was studied to assess the effects on C, N and P mineralization in relation to the fate of tannins by incubation experiments during various time intervals. TA induced a rapid short-term effect resulting in high C respiration and net N and P immobilisation. After one week of incubation, TA was decomposed and net C, N and P mineralization and net nitrification resembled that of the control (non-amended litter). CTs exhibited effects on net mineralization on longer terms, i.e. after several weeks of incubation until the end of the experiment (84 days). While net N and P mineralization were greatly reduced, net nitrification was only slightly affected. Most likely CTs formed complexes with organic N of the substrate thereby reducing net N mineralization, while such complexes were not involved in net nitrification processes. The reduction of net P mineralization is due to the lack of need for P by microbes when they cannot get access to N. The fact that decreasing amounts of extractable CTs were accompanied by increasing effects on mineralization processes with incubation time strongly suggests that CTs were incorporated into the litter in such a way that they were inextricable by the common solvents needed to measure tannins, such as for the Folin–Ciocalteu and HCl–butanol assays.     

Patterns of Carbon, Nitrogen and Phosphorus Dynamics in Decomposing Foliar Litter in Canadian Forests

We examined the patterns of nitrogen (N) and phosphorus (P) gain, retention or loss in ten foliar tissues in a litterbag experiment over 6 years at 18 upland forest sites in Canada, ranging from subarctic to cool temperate. N was usually retained in the decomposing litter until about 50% of the original C remained. The peak N content in the litter was observed at between 72 and 99% of the original C remaining, with C:N mass quotients between 37 and 71 (mean 55). The rate of N release from the litters was not related to the original N concentration, which may be associated with the generally narrow range (0.59–1.28% N) in the litters. P was immediately lost from all litters, except beech leaves, with critical litter C:P mass quotients for P release being in the range 700–900. The rate of P loss was inversely correlated with the original litter P concentration, which ranged from 0.02 to 0.13%. The soil underlying the litterbags influenced the pattern of N and P dynamics in the litters; there were weak correlations between the N and P remaining at 60% C remaining in the litters and the C:N and C:P quotients of the surface layer of the soil. There was a trend for higher N and P retention in the litter at sites with lower soil C:N and N:P quotients, respectively. Although there was a large variation in C:N, C:P and N:P quotients in the original litters (29–83, 369–2122 and 5–26, respectively), and some variation in the retention or loss of N and P in the early stages of decomposition, litters converged on C:N, C:P and N:P quotients of 30, 450 and 16, when the C remaining fell below 30%. These quotients are similar to that found in the surface organic matter of these ecosystems.     

Contribution of Fungi and Bacteria to Leaf Litter Decomposition in a Polluted River

The contribution of fungi and bacteria to the decomposition of alder leaves was examined at two reference and two polluted sites in the Ave River (northwestern Portugal). Leaf mass loss, microbial production from incorporation rates of radiolabeled compounds into biomolecules, fungal biomass from ergosterol concentration, sporulation rates, and diversity of aquatic hyphomycetes associated with decomposing leaves were determined. The concentrations of organic nutrients and of inorganic nitrogen and phosphorus in the stream water was elevated and increased at downstream sites. Leaf decomposition rates were high (0.013 day⁻¹ < k < 0.042 day⁻¹), and the highest value was estimated at the most downstream polluted site, where maximum values of microbial production and fungal biomass and sporulation were found. The slowest decomposition occurred at the other polluted site, where, along with the nutrient enrichment, the lowest current velocity and dissolved-oxygen concentration in water were observed. At this site, fungal production, biomass, and sporulation were depressed, suggesting that stimulation of fungal activity by increased nutrient concentrations might be offset by other factors. Although bacterial production was higher at polluted sites, fungi accounted for more than 94% of the total microbial net production. Fungal yield coefficients varied from 10.2 to 13.6%, while those of bacteria were less than 1%. The contribution of fungi to overall leaf carbon loss (29.0 to 38.8%) greatly exceeded that of bacteria (4.2 to 13.9%).     

天坑森林植物叶-凋落物-土壤C、N、P生态化学计量特征

为探究广西乐业大石围天坑森林群落的C、N、P养分循环特征,比较了天坑内外森林群落的植物叶片-凋落物-土壤C、N、P含量及其化学计量比,采用相关性分析和冗余分析等统计方法研究其内在联系和相互影响。结果表明,与天坑外部森林相比,天坑内部森林植物叶片和凋落物呈现出C低N、P高,土壤为C、N低P高的格局。植物叶片C:N、C:P与凋落物C、N:P显著正相关,植物叶片C与土壤P显著负相关;天坑外部森林的植物叶片N、N:P与土壤N:P显著负相关,植物叶片C:N与土壤C、C:N显著正相关,说明天坑森林内部凋落物的C、P养分可能主要来源于植物叶片,而天坑外部森林的植物叶片C、N主要来自土壤。土壤C:N:P对植物叶、凋落物的C:N:P变化的解释率分别为90.7%和50.6%,其中土壤P对植物叶和凋落物的C:N:P计量特征变化的解释度最高,坑内生境植物对P含量变化更为敏感、坑外植物对于N含量变化更为敏感,表明天坑内部森林可能是P素受限位点、天坑外部森林是N素受限位点。喀斯特天坑内部森林和外部森林植物叶-凋落物-土壤的C:N:P的差异和联系,体现了天坑内外森林群落的养分循环特征和植物群落的适应性。     

三峡水库香溪河库湾春季水华期间悬浮物动态

在三峡水库香溪河库湾春季藻类水华期间开展了水体悬浮物动态研究.调查结果表明：总悬浮物浓度的中位数是6.80 mg·L^-1, 波动范围是0.66～134.92 mg·L^-1,从河口到库尾入库点呈现逐渐递增的趋势;无机悬浮物空间格局与总悬浮物基本相似,而有机悬浮物空间格局与总悬浮物差异较大,与叶绿素a较为相似.回归分析表明：库湾中部水域叶绿素a与总悬浮物、有机悬浮物均有显著的线性关系,分别解释了总悬浮物、有机悬浮物总变异的66.7%～96.7% 和 58.9%～85.5%;在库湾两端（河口与库尾）叶绿素a与悬浮物参数均没有显著的线性关系.在库湾中部水域,有机悬浮物比无机悬浮物更能解释总悬浮物的变异;在库湾两端,无机悬浮物比有机悬浮物更能解释总悬浮物的变异.这意味着库湾中间水域总悬浮物的动态主要受有机悬浮物内源性生产的影响,而河口或库尾总悬浮物的动态主要受外源性的无机悬浮颗粒物输入的影响.     

Differential Controls of Water Input on Litter Decomposition and Nitrogen Dynamics in the Patagonian Steppe

Studies of the effects of precipitation on litter decomposition and nitrogen mineralization in arid and semiarid environments have demonstrated contradictory results. We conducted a manipulative experiment with rainout shelters in the semiarid Patagonian steppe, aimed at assessing the direct effects of water availability on litter decomposition and net nitrogen mineralization while isolating the indirect effects. We created four levels of precipitation input: control and three levels (30, 55 and 80%) of precipitation interception and we examined litter decomposition and nutrient release of a dominant grass species, Stipa speciosa, inorganic soil nitrogen, and in situ net nitrogen mineralization over two consecutive years. Litter decomposition rates (k, year⁻¹) varied significantly (P < 0.001) among precipitation interception treatments and were positively correlated with incoming annual precipitation (APPT, mm/year) (k = 0.0007 × APPT + 0.137). In contrast, net N mineralization was not correlated with incoming precipitation. Soil NO₃⁻ significantly decreased with increasing precipitation input, whereas soil NH₄⁺ concentration did not differ among precipitation interception treatments. Controls of water input on litter decomposition appear to be different from controls on N mineralization in the semiarid Patagonian steppe. We suggest that although water availability affects both the mineralization of C and N, it differentially affects the movement and fate of the inorganic products. A consequence of the accumulation of inorganic N during dry episodes is that periods of maximum water and soil nutrient availability may occur at different times. This asynchrony in the availability of N and water in the soil may explain the observed lags in the response of primary production to increases in water availability.